Conversion of hydrocarbon oils



Oct. 8, 1935. R. F. TROW CONVERSION OF HYDROCARBON OILS Filed May 4,1933 x'ff. 314ML" ATTORNEY pors and residual oils in liquid form aresepa.- 25

Patented Oct. 8, 1935 UNITED ASTATES A PATENT oFFlcE CONVERSION FHYDBOCARBON OILS y Richard FfTrow, Port Arthur, Tex., assignor to TheTexas Company, New York, N. Y.. a corporation of Delaware ApplicationMay 4, 1933, Serial No. 669,301

8Claims.

tillate of high antiknock value and a low yield of heavy distillate orfuel oil from a dirty stock,

that is to say, a stock which cannot be subjected to a drastic crackingoperation producing a high yield of Vgasoline per pass without excessivecoke formation. y

My invention has for further objects such additional improvementsinoperative advantages and results as may hereinafter belfound to obtain.

My invention is especially applicable to an operation conducted for thepurpose of converting hydrocarbon oils to oils of lower boiling point inwhich a stock is subjected to cracking conditions of temperature andpressure, as for example, while passing through a heating coil, thecracked products being delivered to one or more enlarged reactionvessels or stills from which varately withdrawn, and more especially tooperations in which liquid is withdrawn from the reaction vessel orvessels at a rate sumcient to prevent liquid from accumulating withinthe reaction vessel or vessels and topreventdigestion of liquid withinthe same, while permitting digestion of vapors therein at a crackingtemperature.y

' My invention contemplates heating a charging stock, such, Vforexample, as a dirty gas oil or a reduced crude resulting from a previoustopping operation, to Aa moderate cracking temperature and soaking theheated stock, preferably in a separately fired soaking coil, to break orreduce the viscosity of the stock without causing deposition of coke toan undesirable extent, and discharging the viscosity broken stream intoa distilling zone supplied with hot vapors produced elsewhere in thesystem. In the distillation zone, the more volatile constituents of theviscosity-broken stream are vaporized and the resultant vapors, togetherwith other vapors from the distillation zone, are fractionated ordephlegmated, for exampie, by indirect contact with a stream ofrelatively cool charging stock or by reuxing with a suitable oil, torecover therefrom a clean gas-oil indicated, that is to say, atrelatively high temperature and preferably in the vapor phase, thecracked products being delivered to one or more enlarged reactionvessels or stills from which unvaporized or residual liquid ispreferably withdrawn at a rate sumcient to prevent accumulation ofliquid in the reaction vessel or vessels. The residual liquid thuswithdrawn may be treated for the recovery of the more volatileconstituents thereof, while the vapors pass to the distilla- 10 tionzone where they are brought into contact with the viscosity-brokencharging stock.

Unvaporized oil collecting within the distillation zone may be deliveredto one or more of the reaction vessels or stills, either directly or byl5' being commingled with the stream of cracked products entering thesame from the high-temperature or vapor-phase cracking coil.

My invention further contemplates cooling a portion of the clean gas oilor other interme- 2,0 diate fraction recovered by fractionation anddephlegmation of the vapors as set forth hereinabove, and the deliveryof the resultant cool oil to the distillation zone for purposes ofdephlegmation and to prevent coking.

With regard to the conditions under which the viscosity breaking of thecharging stock is carried out, it may be said that, in general, thetemperature employed will be suflicient to produce a material reductionof the viscosity of the charging stock without causing the deposition ofcoke to a material extent and to effect a hunted amount of cracking perpass, for example, from 6% to 8% of gasoline per lpass and at the most vnot over 12% of gasoline per pass. The effect of 35 this treatment is,however, to make it possible ultimately to obtain larger yields ofvaluable light cracked distillate from a dirty charging stock withoutexcessive coke formation.

In order that my invention may be clearly set 40 forth and understood, Inow describe, with reference to the drawing accompanying and formingpart of this specication, a preferred manner in which my invention maybe practiced and embodied. In this drawing, 45

The single gure is a more or less diagrammatic elevationalview ofapparatus for accomplishing the conversion of hydrocarbon oil to oils oflower boiling point in accordance with my invention. 5 In the drawing,there is illustrated a furnace I having a high-temperature hea-ting coil2 and three enlarged reaction vessels or stills 6, 1`, and 8, althoughit will be readily understood by those skilled in the art tha-t thenumber of suchfves sels or stills may be varied in accordance with therequirements of individual instances. The distillation zone referred tohereinabove is located Within a suitable vessel I0 having baiiles I I,and the dephlegmation and fractionation of vapors removed from thevessel III is carried out in a suitable fractionating tower I2 which maybe provided with a plurality of gas-and-liquidcontact trays or the like.shown diagrammatically at I3. Many specific forms of suitable trays areknown in the art and n o particular type need be described here indetail. i

Further dephlegmation of vapors not condensed in the fractionating towerI2 may be accomplished in a dephlegmator I4 provided with aheat-exchange coil I5. As shown, the apparatus additionally comprisesthe condenser I6, a gas separator I1, cooling coils I8 and I9 andvarious conduits or transfer lines, valves and pumps which will bereferred to hereinbelow.

In practicing my invention, a charging stock, such,' for example, as adirty gas oil, a reduced crude or a mixture thereof, is withdrawn from asouice (not shown) through a conduit 2I by means of a pump 22 and mayinitially be passed in the manner indicated in the drawing through theheat-exchange coil I5, where, by indirect contact with vapors passingthrough the dephlegmator I4, the temperature of the charging stock maybe brought to from 400 to 450 F. It will, however, be understood that ifthe charging stock is already in a heated condition there will be noadvantage in passing the stock through the heatexchange coil I5 and thisstep may then be omitted. In the latter event, however, it is desirableto supply a suitable reflux oil to the fractionating tower I2.

'I'he heated charge oil then passes under elevated pressure through aconduit 23 to the economizer coil 3 within the furnace I, where thetemperature of the charging stock is raised to a point sufiicient tosupport a moderate cracking or viscosity-breaking effect, for example,from 820 to 880 F., and preferably about 660 F.

The heated charging stock flows from the economizer coil 3 through aconduit 24 to the soaking coil 5 located within the furnace 4.Preferably, merely suilicient heat is provided in the furnace 5 tomaintain the charging stock within the desired temperature range inorder to complete the viscosity-breaking operation. However, if for anyreason the oil should leave the economizer coil 3 at a temperature lowerthan the desired cracking temperature, sufliclent heat may be suppliedto the tubes forming the rst portion of the coil 5 through which thestream passes to raise the oil to the desired temperature, and the oilis then soaked for a sufficient time at this temperature in theremaining portions ofv -the coil 5.

The viscosity-broken stream leaving the coil 5 then passes through atransfer line 25 to the distillation vessel I0, which it enters at anintermedia-te point.

Within the vessel I6, the viscosity-broken stream is subjected to directcontact with hot vapors from the still 8 entering the lower portion ofthe vessel I6 through a. conduit 25, and a combined volatilizing anddephlegmating effect occurs,.resultingvin the vaporization of the morevolatile constituents of the viscosity-broken stream. The combinedvapors reaching the top of the distillation vessel I0 pass through avapor line 21 to the lower part of the fractionating tower I2, wheredephlegmation is carried out to a sufilcient extent to produce a liquidfraction comprising a gas oil or the like which collects 5 lin 'thelower portion of the fractionating tower I2 and is withdrawn through aconduit 28. A portion of this gas-oil fraction may be withdrawn througha branch conduit 29 having a valve 3I and after being cooled in thecooling coil 10 I8 may be delivered by means o! a pump 32 and a reiiuxline 33 to the upper part of the distillation vessel I0 in sumcientamount to provide a limited dephlegmation of the vapors within thelatter and to prevent the formation of coke on 15 the bailles II.

The remaining portion'of the clean gas oil fraction or recycle stockremoved from Ithe bottom of the fractionating tower I2 is withdrawnthrough abranch conduit 34 having a valve 35 and 20 is delivered bymeans of a pump 35 and a conduit 31 to the vapor-phase cracking coil 2locatedv in the furnace I, where it is heated to a temperaturesufficient to effect vapor-phase cracking, preferable at a high rate ofcracking per pass, for example 25% or more. ThusI may employternperatures of from 900-to l000 F. and preferably about 915 F. Thecracked products then pass through a transfer line 39 which may beprovided as shown with a pressure-reducing valve 4I -to the upper partof the still 6. Within the still 6 a separation of vapors and liquidoccurs. the vapors, and it may be a small amount of liquid oil, passingthrough a conduit 42 into the adjacent still 1. A further separationoccurs in the latter and the vapors pass to lthe third still 8 throughan overhead conduit 43.

As recited hereinabove, unvaporized liquids which tend to collect in thestills, 6, 1, and 8 are withdrawn from the latter by means of drainconduits 46, 41, and 48, having float-operated valves 5I, 52, and 53,respectively, at rates sumcient to prevent accumulation of liquid withinthe vessels or stills 6, 1, and 8. Preferably, merely enough liquid ispermitted to collect within the 45 vessels 5, 1, and 8 to form a seal toprevent escape of vapors from the bottoms thereof. The residual oil ortar thus withdrawn is preferably delivered through a conduit 53a to atar stripper 59 to be described more fully hereinbelow. 50

The unvaporized portion of the viscosity-broken stream delivered to thedistillation vessel I0, together with any condensate obtained from thevapors entering the distillation vessel I0 through a conduit 26, iswithdrawn from the lower part 55 of the distillation vessel I0 through aconduit 55 and delivered by means of a pump 56 through a conduit 51having a valve 58 to the transfer line 39, or it may be delivereddirectly to the stills 6,

8, and 1. The residual oil thus withdrawn from 60 the bottom of thedistillation vessel I0 may have a high temperature, for example around850 F., and in treating certain stocks, a portion of the stream leavingthe pump 55 may be by-passed through a line 6I having a valve 63 to thecooler 65 I9 and thence to the inlet side of the pump 55. In thisinstance, sufficient cooling is eiected in the cooler I 9 to reduce thetemperature of the oil reaching the pump 56 to, for example, around 800F. or even lower. 70

In the preferred method of operation, the introduction of combinedcondensate and residual portions of the charging stock, whether cooledor not, to the transfer line 39, is so regulated as to maintain atemperature of from about 870 to 75 about 830 Il'. in the stills 8, 1,and 8, maintenance of this temperature range facilitating the withdrawalof liquid from the stills '6, 1, and 8 and the maintenance of low liquidlevel" conditions therein.

' The uncondensed vapors leaving the dephlegmator I4 pass through avapor line 65 to the conv denser I6 where they are cooled in the usualman- -ner, the cooled products then passing through a line L66 to theseparator I1.` Gas and any uncondensed vapors are removed from theseparator I1 through a conduit 61 having a valve 68, while light crackeddistillate is removed from the separator I1 through a line 08. A portionof this condensate may be returned through a branch conduit 1I having avalve 12 and a pump 18 to the upper part of the fractionating tower I2kas a re-y flux. while the remaining portion or it may be all of thecondensate from the separator I1 passes through a conduit 14 having avalve 1l to storage or to suitable apparatus for effecting stabilizationthereof.

'Ihe -pressures maintained within the system may vary considerably butin general the pressures in the coils 2, 8 and 5 are maintained within asuitable range, for example, from 200 to 600 pounds per square inch.While similar pressures may be maintained throughout the system, it isyordinarily preferred to maintain somewhat lower pressures, for example,from 150 to 350 pounds vpersquare inch, in the stills6, 1, and 8, thedistillation vessel I0 and the fractionating tower- I2. In a modifiedform of my invention the pressure in the dephlegmator I0 andfractionating tower I2 may be reduced to 150 pounds per square inch, orevenlower, by means of 'a pressure-reducing valve 80' located inthevconduit 26.-

` As has been stated hereinabove the liquid withdrawn from the stills 6,"I, and 8 is preferably passed through a conduit 68a to a tar stripper64. The tar stripper 84 may be varied in design but in the preferredinstance illustrated it'comprises a flash chamber 6I having bailles 82and a fractionating section 88 having suitable plates or trays 84. Thechamber 8| and the fractionating section 84 are separated by a trap-outtray 8l and the upper portion of the fractionating section 84 isprovided with a reflux inlet line 86.

The liquid withdrawn from the stillsv6, 1, and 8 in this instance passesthrough the conduit 53a wherein is located a pressure-reducing valve 81by means of which the oil is reduced in pressure as it passes into theflash chamber 8 I The lower boiling constituents ofthe oil are therebyliberated in vapor form and passed upward into the fractionating section83 through a vapor line 88 while heavy residual portions of the oil arewithdrawn from the bottom of the iiash chamber 8| through a conduit 80having a valve 8| and pref- A erably leading through a cooler 82 to fueloil storage facilities (not shown). u

By means of reflux introduced through the line v86 or by cooling eiectedin any other suitable manner the vapors passing through thefractionating section 83 or the tar stripper 54 are subjected tofractional condensation to such an extent as to effect the separation inliquid form of a'heavy gas oil fraction which is withdrawn from thetrap-out tray 85 through a conduit 88 having the line 23 to the inlet ofthe coil 8, being thus therein.

The vapors remaining uncondensed at the top of the fractionating section88 of the tar stripper s 64 pass through a conduit 81 to a condenser 88where they are cooled to eifect a condensationof normally liquidconstituents, the operationpreferably being conducted to recover at thispoint a distillate comprising either heavy 'naphtha constituents orlight gas oil constituents or a mixture of these. The mixture ofuncondensed gases and condensate then passes through a conduit 88 to agas separator I8| having a valved outlet |82 through which uncondensedgases escape. The condensate' passes out of the separator |8| through aconduit |08 having a pump |04, by means of which it may be partlyreturned through the conduit 86' wherein is located a valve |08 to thetar stripper 84 as reflux. The remaining portion of the condensaterecovered in the separator |0|, or it may be all of vthis condensate, ispreferably delivered by the pump |04 through the conduit |88 andaconduit |86 having a branch |01 wherein is located a valve |88. 25 tothe conduit 81 where it is commingled with gas oil recycle stockwithdrawn from the bottom of the fractionating tower I2 and beingdelivered to the cracking coil 2.

In an alternative method of procedure, a portion or all of thecondensate withdrawn from the separator I0| may be returned throughconduits |08 and |06 and a branch conduit |09 having a valve ||0 to thefractionating tower I2 for use as reiiux therein. 35

It will be obvious to those skilled in the art that my invention is notlimited to the specic details of the illustrative example or examplesset forth and described hereinabove but may variously be practicedwithin the scope of the claims hereinafter made.

What I claim is:

1. The process of converting hydrocarbon oil into oils of relatively lowboiling points which comprises heating a charge oil to a mild crackingtemperature and soaking the heated oil substantially without reductionof temperature in a primary cracking zone to reduce the viscosity of theoil, passing the viscosity-broken products directly to a distillationzone into direct contact with hot vapors produced in the system, therebyvaporizing lighter fractions vof said viscositybroken products, passingvapors from said distillation zone to a fractionating zone anddephlegmating said vapors to recover therefrom a 55 light distillate anda heavier recycle stock fraction, subjecting said recycle stock torelatively drastic cracking conditions in a separate cracking zone,discharging the cracked products into therst of a plurality of enlargedreaction vessels 30 'arranged in series in each of which separation of ivapors from liquid products of reaction occurs, conducting separatedvapors from one reaction chamber to the others in succession and fromthe last reaction chamber to said distillation zone, separatelywithdrawing separated liquid from each of said reaction chambers,withdrawing residual oil from said distillation stage and directing itto said series of enlarged reaction vessels.

2. The process vof converting hydrocarbon oil into oils of relativelylow boiling points which comprises-heating a charge oil to a crackingtemperature of the order of 820 F.-880 F. and soaking the heated oilsubstantially without reduction of temperature in a primary crackingzone broken products, dephlegmating the evolvedv vapors from saiddistillation zone to recover therefrom a light distillate and a heaviercondensate, subjecting said heavier condensate to heating to eiect ahigh rate of cracking per pass in a. separate cracking lzone anddirecting the cracked products into an enlarged reaction zone,v

conducting residuefrom said distillation zone into said reaction zone,maintaining a temperature therein of the order of 870-930P F.,witldrawling liquid constituents from said reaction zone at a rateadequate to prevent accumulation of liquid therein passing vapors fromsaid reaction zone to a second reaction zone wherein the vapors aremaintained at cracking temperature to eiect further cracking anddirecting vapors from said second reaction zone.

3. The process of converting hydrocarbon oil into oils of relatively lowboiling points which comprises passing cycle condensate formed in theprocess through a high temperature heating coil wherein the condensateis heated at temperatures of the order of 900 F.-1050 F. to subject theoil to a high rate of cracking per pass, discharging the products fromsaid heating coil -into an enlarged reaction zone maintained undercracking conditions and wherein separation of vaporfrom liquid occurs,withdrawing liquid constituents from. said reaction zone at a rateadequate to prevent the accumulation of liquid therein, passing only theseparated vapors into a second reaction zone wherein the vapors aremaintained at cracking temperature to effect further cracking, directingvapors from said second reaction zone to a distilling zone, heatingcharging stock in a primary cracking zone to a cracking temperature ofthe order of 820 F.-880 F. under conditions to effect a cracking perpass into gasoline constituents of about 6%-8% and effect a reduction inthe viscosity of the charging stock, delivering the viscosity-brokenproducts directly to said distilling zone into contact with aforesaidseparated vapors introduced thereinto to eiiect distillation of theviscosity-broken products and condensation of a portion of saidseparated vapors, withdrawing from said distilling zone a liquid residuecomprising residual constituents of said viscosity-broken products anddirecting said liquid residue to said enlarged reaction zone wherein itis in contact with the heated products discharged thereinto from thesaid high temperature heating coil and subjecting vapors evolved fromsaid distilling zone toA fractionation to separate out a lightdistillate and a heavier condensate constituting the cycle condensatepassed to the cycle condensate heating coil.

4. 'I'he process of converting hydrocarbon oil into oils of relativelylow boiling points; which comprises passing cycle condensate formed inthe process through a high temperature heating coil to subject thecondensate to a high rate of cracking per pass, dischargingthe productsfrom said heating coil into an enlarged reaction zone maintained undercracking temperatures of the order of 870 F.930 F. and whereinseparation of vapor from liquid occurs, passing only the separatedvapors into a second reaction zone wherein the vapors are maintained atcracking temperature to effect further cracking, directingv vapors fromsaid second reaction zone to a distilling zone, heating charging stockin a primary cracking zone to a cracking temperature of the 5 order of820 F.880 F. under conditions to efiect a cracking per passinto-gasoline constituents of about 6%'8% and effect reduction in theviscosity vot the charging stock, delivering the -viscosity-brokenproducts directly to said distill- 10 ing zone into contactwithaforesaid separated vapors introduced thereinto to eiectdistillation of the viscosity-broken products and condensation of a'portion of said separated vapors, withdrawing from said distilling zonea liquid residue comprising residual constituents of saidviscositybroken products and directing said liquid residue to saidenlarged reaction zone wherein it is in contact with the heated productsdischarged thereinto from the said high temperature heat- .ing coil,withdrawing liquid from said enlarged reaction zone at a rate adequateto prevent the pors evolved from said distilling zone to fractionationto separate out a light distillate and a heavier condensate constitutingthe cycle condensate passed to the cycle condensate heating coil.

5. Apparatus for cracking hydrocarbon oils that comprises a crackingstill, a distilling chamber adapted to receive vapors from the crackingstill, a ifra'ctionating tower adapted to receive vapors from thedistilling chamber and separate out condensate therefrom, a furnaceformed to prgwide a main heating section and an economizer section, ahigh temperature cracking coil located in the main heating section ofthe furnace, means for conducting condensate from the fractionatingtower to the high temperature cracking coil, a transfer line forconducting the products from the high temperature cracking 40 coil tothe cracking still, a low temperature cracking coil located in theeconomizer section of said furnace, means for introducing charging stockto said low temperature cracking coil, a soaking coil adapted to receivethe products from said low temperature cracking coil, means independentof said furnace for maintaining the soaking coil at a crackingtemperature, means for conducting products from the soaking coil to saiddistilling chamber and means for conducting liquid from the distillingchamber to said cracking still.

6. Apparatus for cracking hydrocarbon oils that comprises a crackingstill, fractionating means for separating out a condensate from vaporsevolved from the cracking still, a furnace formed to provide a mainheating section and an economizer section, a high temperature crackingcoil located in 'the main heating section of the furnace, means forconducting condensate from the fractionating means to the hightemperature cracking coil, a transfer line for conducting the productsfrom the high temperature cracking coil to the cracking still, a lowtemperature cracking coil located in the economizer section of saidfurnace, means for' intro- 65 ducing charging stock to said lowtemperature cracking coil, a soaking coil adapted to receive theproducts from said low temperature crackaction zone where separation ofvapor from liquid residue occurs and wherein the liquid residue issubjected to flash distillationin a flashing zone, the vprocess thatcomprises heating charging stock in a primary cracking orviscosity-breaking coil to a cracking temperature to eiect a reductionin the viscosity thereof, delivering the viscositybroken products into adistilling zone, passing vapors from. said enlarged reaction zone intosaid distilling zone into contact with said viscositybroken productsthereinA to effect distillation of 'the viscosity-broken products andcondensation of a portion of said vapors, subjecting the remainingvapors to fractionation to separate out alight distillate and a cyclecondensate, passing said cycle condensate to a high temperature crackingcoil wherein the oil is subjected to a relatively high crackingtemperature to effect a high rate of cracking per pass and directedthence into aforesaid enlarged reaction zone, subjecting the vaporsevolved in the' flashing zone to fractionation to separate out a lighterfraction and heavier fraction thereof, directing the heavier fraction tosaid viscosity-breaking coil and passing the lighter fraction to saidhigh temperature cracking coil.

8. In the conversion oi.' hydrocarbon oil into oils of lower boilingpoints wherein hydrocarbon oil is subjected to cracking in an enlargedreaction zone where separation of vapor from liquid residue occurs andwherein the liquid residue is subjected to flash distillation in aflashing zone, the process that comprises heating charging stock in aprimary cracking or viscosity-breaking coil to a cracking temperature toeffect a reduction in the viscosity thereof, delivering theviscositybroken products into a distilling zone, passing vapors fromsaid enlarged reaction zone into said distilling zone into contact withsaid viscositybroken products therein to effect distillation of theviscosity-broken products and condensation of a portion of said vapors,subjecting the remaining vapors to fractionation to separate out a lightdistillate and a cycle condensate, passing said cycle condensate to ahigh temperature cracking coil wherein the Oil is subjected to arelatively high cracking temperature to effect a high rate of crackingper pass and directed thence into aforesaid enlarged reaction zone,withdrawing from said distilling zone a liquid residue comprisingresidual constituents of said viscositybroken products and directingsaid liquid residue to said enlarged reaction zone wherein it is incontact with the heated products discharged thereinto from said hightemperature cracking coll, subjecting the vapors evolved in the flashingzone to fractionation to separate out a lighter fraction and heavierfraction thereof, directing the heavier fraction to saidviscosity-breaking coil and passing the lighter fraction to said hightemperature cracking coil.

RICHARD F. TROW.

CERTIFICATE 0F CORRECTION.

iatent No. 2,016, 950.

October 8, 1935.

RICHARD F. TRow.

lt is hereby certified that error' appears in the printed specificationof the above numbered patent requiring correction as follows: Page 4,first column, line 24, claim 2, after "zone" insert the words to saiddistilling zone; and that the said Letters Patent should be read withthis correction therein that the same may conform to the record of thecase in the Patent Office.

. Signed and sealed this 19th day of November, A. D. 1935.

l I Leslie Frazer (Seal) Acting Commissioner of Patents.

